A polyoxyalkylene polymer having a reactive silyl group is a polymer capable of reacting with water in the air at room temperature to be cured into a rubbery form, has already been produced industrially, and is widely used in applications such as sealants, adhesives, and paints.
In a curable composition comprising a polyoxyalkylene polymer having a reactive silyl group, a phthalic acid ester plasticizer is used for the purpose of improving the workability of the curable composition and for the purpose of adjusting the mechanical properties of a cured product (Patent Literature 1).
However, in recent years, the phthalic acid ester plasticizer is regarded as a substance suspected to have an endocrine-disrupting effect, and the effect of the phthalic acid ester plasticizer on the environment and the ecosystem is considered an issue, so that use of the phthalic acid ester plasticizer is limited.
Therefore, recently, a terephthalic acid ester plasticizer may be used as a substitute for the phthalic acid ester plasticizer (Patent Literature 2, Patent Literature 3).
In addition, a curable composition comprising, as a plasticizer, a methyl ester plasticizer such as dimethyl adipate is also known (Patent Literature 4, Patent Literature 5).